Currently, coordinating a transaction "hops" between the TransactionCoordinatorService's ThreadPool and the fixed ThreadPoolTaskExecutor on the Grid.

It does so in order to run the parts of the commit coordination that block on the local storage engine in a separate thread pool from the Grid's fixed ThreadPoolTaskExecutor.

This ticket is to make coordinating the transaction run wholly on the fixed ThreadPoolTaskExecutor on the Grid, and set the size of the thread pool in that ThreadPoolTaskExecutor to unbounded.